U.S. Pat. No. 6,155,754 relates to a fastening arrangement in a cutting tool, having a standard cutting insert and a special locking screw, the screw head having two opposite, vertical chamfers. In this arrangement, the cutting insert can be removed without completely unscrewing the locking screw from a threaded hole in the cutting insert seat.
A drawback with this arrangement is that the screw head is not symmetrical and consequently the screw thread and the bore thread have to be designed accurately enough to ensure that after the screw is fastened, the screw head abutment surfaces are correctly oriented in order to abut and secure the cutting insert in its seat.
Another drawback is the weakening of the screw head as a result of the removal of material due to the chamfering. Consequently, less torque can be applied to the screw head than in comparison with a non-chamfered screw head. This may lead to unpredicted, unwanted effects such as inaccuracies in locating the cutting insert, or a sudden release of the insert.
U.S. Pat. No. 4,397,592 describes a fastening arrangement for cutting inserts having a standard cutting insert and a locking pin, asymmetrically clamping the cutting insert. This arrangement allows indexing of the cutting insert by only loosening the locking pin, lifting it until its cylindrical portion is out of its corresponding portion in the receiving hole and tilting the locking pin until it is possible to slide the cutting insert coaxially over the clamping head.
A certain drawback of this arrangement is the small and asymmetric abutment area between the locking pin clamping head and the locking face of the insert aperture. This asymmetry leads to asymmetric force distribution in the cutting insert, in comparison to the symmetric abutment. This may lead to locating inaccuracies, shortened life of the cutting insert or breaks in the cutting edges.